Preheat oven to 350°F (175°C).
Line your muffin tin with paper liners.
In a bowl, mash bananas until smooth.
Add eggs, butter, vanilla, and sugar.
Whisk until ingredients are well combined.
In another bowl, whisk flour, soda, salt, and cinnamon.
Add dry mix to wet mixture slowly.
Stir gently with a spatula until just mixed.
Fold in nuts or chocolate chips if using.
Scoop batter evenly into muffin cups.
Bake for 18-22 minutes until golden brown.
Insert toothpick—it should come out clean.
Cool muffins in tin for 5 minutes.
Transfer to a rack to cool fully.
Transfer to a rack to cool fully.